CM_1992_H_20.pdf (8.065Mb)

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This report not to be quoted without prior reference to the Council*

International Council for the Exploration of the Sea

C.M.1992/H:20 Pelagic Fish Committee Ref.: Demersal Fish

&

Hydrography Committees

REPORT OF THE INTERNATIONAL BOTTOM TRAWL SURVEY IN THE NORTH SEA, SKAGERRAK AND KATTEGAT IN 1992: QUARTER 1

by

The International Bottom Trawl Survey Working Group

This document is a report of a Working Group of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council. Therefore, it should not be quoted without consultation with the General Secretary.

*General Secretary

ICES

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CONTENTS

1 I N T R O D U C T I O N . . . 1

2 SURVEY METHODS AND PARTICIPATION. . . 1

3 DATA AVAILABLE . . . 1

4 STANDARD OUTPUT FROM THE ICES IYFS DATA BASE . . . 1

5 RESULTS GOV-TRAWL FOR 1992 . . . 1

5.1 North Sea . . . 1

5.2 Skagerrak-Kattegat (Division Ilia) . . . 3

6 RESULTS OF SAMPLING OF LARVAE IN 1992 . . . 4

7 HYDROGRAPHIC DATA . . . 4

7.1 Hydro-chemistry Survey . . . 4

7.2 UKDMA . . . 4

8 REFERENCES . . . 5

9 TABLES. . . 6

10 FIGURES . . . 13

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1 INTRODUCTION

This report presents the final results for the International Bottom Trawl Survey in February/March 1992, formerly known as the International Young Fish Survey (IYFS).

In 1990 it was decided to combine the effort of the International Young Fish Survey with a number of national surveys such as the English and Scottish Groundfish Surveys into a quarterly coordinated bottom trawl survey, to be held for a period of 5 years (ICES C.Res.1990/4:3). These quarterly surveys started in 1991.

Country Vessel Period

The data in this report comprise the bottom trawl catches of the seven standard species (herring, sprat, mackerel, cod, haddock, whiting and Norway pout), as well as the catches of herring and sprat larvae. Also summarized results of temperature and salinity sampling are presented.

2 SURVEY METHODS AND PARTICIPATION For all matters on survey methodology, the reader is referred to the Manual of which a revision has been prepared this year (Addendum to ICES, Doe. C.M.

1992/H:3). Details on the participation in the 1992 survey are given below.

Number of hauls

GOV MIK/IKMT

Denmark "Dana" 30.01/17.02 40 97

France "Thalassa" 13.01/28.01 53 0

Germany, F.R. "W. Herwig" 31.01/18.02 62 0

"Solea" 08.02115.02 31 0

Netherlands "Tridens" 04.02.26.02 45 51

Norway "G.O. Sars" 26.01/10.02 4965 65

Swweden "Argos" 03.02/20.02 47 58

UK (Scotland) "Scotia" 30.01/01.03 64 44

3 DATA AVAILABLE

In Table 3.1 is shown for which surveys data presently are available in the ICES IYFS Data Base.

At the time of the analysis of the 1992 survey presented in this report all final data were available in the data base.

4 STANDARD OUTPUT FROM THE ICES IYFS DATABASE

For details on the standard analysis of the data the reader is referred to a description by Pedersen (1989).

At request copies of this paper are available at the ICES Secretariat.

5 RESULTS GOV-TRAWL FOR 1992 5.1 North Sea

Preliminary indices based on certain size classes (herring

<20 cm, sprat < 10 cm, mackerel <20 cm, cod

< 25cm, haddock < 20 cm, whiting < 20 cm and Norway pout

<

15 cm) and the indices used by the Assessment Working Groups are compared with the fmal indices in Table 5 .1. The preliminary indices are, as in most years, very close to the final ones. Final indices of 1- and 2- group fish of the seven standard species are given in Table 5.2. Table 5.3 gives the mean age composition of the standard species within the relevant standard areas.

The number of hauls used in the analysis of the herring data and the hauls used for the other species are shown in Figure 5.1 and 5.2. The total number of hauls in the North Sea was 329 of which 270 were daylight hauls which were used for the analysis of the herring data. In Skagerrak and Kattegat a total of 46 daylight hauls was carried out which gives a grand total of 375 valid hauls.

Per species there is a set of figures showing the distribu-

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1-group fish per rectangle. For each species a specific standard area is used to calculate the index of year class strength. This area is indicated in the figures. In case of 2-ringed herring it should be noted that the indices are based on all rectangles in the North Sea

HERRING

The indices for age groups 1 and 2 are given in Table 5.2 and the mean number per one hour trawling of 1-, 2- and 3

+

ringers is shown in Figures 5.3 to 5.5. The mean length of the 1-ringers per rectangle is presented in Figure 5.6.

The abundance of 1-ringed herring was slightly below the average of the 10 preceding year classes. The age group was distributed in the usual areas in the southern and central North Sea.

Two-ringed herring were less abundant than in most previous years. The largest catches were taken in the central and southern North Sea. Few 2-ringed herring were caught in waters north of 57 oN.

SPRAT

Sprat indices of 1- and 2-group are given in Table 5 .2.

The distributions of the same age groups and the 3

+

group, as well as the mean length of 1-group per rectangle, are shown in Figures 5. 7-5.10.

There was an increase in abundance of 1 year-old sprat compared to the two previous years. This age group was fairly abundant in the waters around the Dogger Banlc The index of 1,561 for year class 1991 is the second highest in the time series starting with year class 1971.

Two year-old sprat occurred in the same areas as the younger age group. The abundance of two-year-olds showed an increase compared to the previous year.

MACKEREL

Indices for mackerel are given in Table 5. 2 and the distributions of 1-, 2- and 3

+

group is shown in Figures 5.11-5.13. The mean length of the 1-group per rectangle is presented in Figure 5.14.

The index for age-1 mackerel of 16.0 has a very low precision, due to the extremely high variance on the individual hauls. It seems, however, that one-year-old mackerel are getting increasingly common in the North Sea during winter, especially in the northeastern part.

2

Abundance indices are given in Table 5.2, the distributions of 1-, 2-, and 3

+

group and the mean length of 1-group fish are given in Figures 5.15-5.18.

The 1991 year class of cod caught during the 1992 survey were widely distributed throughout the central North Sea. This pattern of one-year-old cod catches was similar to that found during the 1984, 1986 and 1989 · surveys and along with these three years the 1992 survey has produced one of the four highest index values from the last 12 years. In terms of recent one-year-old indices it is approximately five times greater than for the 1990 year class, four times greater than that for the 1989 year class and equal to the 1988 year class. It is, however, still below the overall series average.

Catches of the 1990 year class as two-year-old fish were well dispersed throughout the survey area, as has been the usual recent pattern, but with no rectangle average number per hour, within the standard area, exceeding 29 fish. The index value, at 4.5, was well below the long term average but indicated a stronger year class than the one-year-old index value of the same year class had done. High catches of this year class, both at age one and at age two, were made in rectangles outside the standard area (see also Anon. 1991). This may suggest that both index values were an underestimate of the year class strength.

HADDOCK

Abundance indices are given in Table 5.2, the distributions of 1-, 2- and 3

+

The index value for one-year-old haddock was the second largest in the whole series and was one of only four to exceed 1,000 (1973, 1974 and 1983 year classes). It was almost two times greater than the value for the 1990 year class and over five times greater than that for either the 1989 or 1988 year class. The fish were well distributed throughout the northern and central parts of the standard area but, unusually, the higher average numbers per hour per rectangle were predominantly in the east and north of that area.

The two-year-old index value was slightly above the long term average and supported the strength of the 1990 year class as one-year-olds. The distribution of two-year-old fish was generally similar to that of the one-year-olds.

WHITING

Abundance indices are given in Table 5 .2, the distributions of 1-, 2- and 3

+

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The index value of 916 of the 1991 year class, almost twice the long term average, is the fourth highest recorded. With three of those high values having occurred in the last four years, this continues the trend in strong year classes of whiting. The higher numbers per hour per rectangle were, as usual, predominant in the central part of the standard area. Unusual, however, were the good catches made in the northern North Sea and this was the first survey in ten years to have produced a non-zero average number per hour in every North Sea rectangle that was fished.

The two-year-old fish followed the normal recent distribution pattern with the larger catches being made in the south-eastern, west-central and north-western parts of the standard area. The index value was almost twice the series average and supported the indication of a strong 1990 year class made by the 1991 one-year-old estimate.

NORWAY POUT

Abundance indices are given in Table 5.2, the distributions of 1-, 2- and 3+ group and the mean length of 1-group fish are given in Figures 5.27-5.30.

One-year-old Norway pout were well distributed throughout the central and northern parts of the standard area with several rectangles east of 0° having high average numbers per hour. These factors combined to pro- duce the highest index value recorded during the 18 year series of Norway pout data. The abundance of the 1991 year class was more than twice that of the 1990 year class, almost four times that of the 1989- and two and a half times that of the 1988 year class.

The abundance of the two-year-olds was 24% above the long term average, compared with the abundance of the same year class as one-year-olds which was 10% below the long term average. The higher catches were made in the eastern and northern parts of the main body of the standard area.

5.2 Skagerrak-Kattegat (Division lla)

The number of hauls per rectangle for herring and gadoids is shown in Figure 5.1 and 5.2. In all 46 hauls were carried out and all standard rectangles were fished.

The final indices for 1- and 2-ringed herring and 1- and 2 + group sprat are given in Table 5 .4. The herring indices are calculated as the mean catches in four depth strata, covering the depth range of 10 - 150 m, and weighted by the surface area of each stratum. Details of the analysis and separation of spring- and autumn spawners are given in the 1989 report (Anon., 1989).

Age/length keys for cod are available from the 1981 IYFS and onwards. The stocks of cod in Skagerrak and Kattegat are assessed separately and indices are given for each area. Final and preliminary indices for cod and preliminary indices for whiting and haddock are given in Table 5.5.

The distribution of herring, sprat and cod is included in the figures in Section 5 .1.

HERRING

The indices are given in Table 5.4 and the distribution is shown in Figures 5.3-5.5. The mean length of 1-group is shown in Figure 5. 6.

The mean index of 1-ringed herring was 5, 057. This value is rather high considering the relatively low index for the North Sea. In previous years, the Skagerrak-- Kattegat seemed to act as an "overflow area" for the North Sea. High indices in Skagerrak-Kattegat only occurred in years of abundant North Sea year classes.

A111-ringed herring in 1992 was classified as North Sea autumn spawners.

Two-ringed herring were less common than in previous years. Based on length and vertebral counts, about 40%

of the 2-ringers was classified as spring spawners.

The index of 1- and 2 + group sprat is given in Table 5.4 and the distribution of 1-, 2- and 3 + group is shown in Figures 5.7-5.9. The mean length of 1-group sprat per rectangle is presented in Figure 5.10.

The index of 5,380 for 1 year-old sprat is the second highest in the time series starting in 1974. This suggests that sprat in Skagerrak-Kattegat is increasing again after several years of low abundance. The index for 2-year-- olds, although higher than in the two previous years, is still below the long-term average.

Preliminary and final indices are given in Table 5.5. The index value for the one-year-old cod in the Skagerrak, as the highest on record and three times greater than the long term average, indicates a strong 1991 year class. In the Kattegat, however, the indications are for one of only average strength.

The estimates from the 1991 survey of a very poor 1990 year class in both areas were further supported by the catch levels of two-year-old fish during the 1992 survey.

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HADDOCK

Haddock of

<

20 cm were abundant in the Skagerrak but less so in the Kattegat. The index value was the highest recorded in the 13 year series and, at four times greater than the long term average, indicated a strong 1991 year class.

WHITING

High catches of

<

20 cm whiting were made throughout Division Ilia, providing the fourth highest index value of the 18 year series. This continues the previous six years trend in strong year classes of whiting.

6 RESULTS OF SAMPLING OF LARVAE IN

1992

The change of standard gear from the IKMT to the ring-framed fme meshed MIK was nearly complete this year. Only "Scotia" used the IKMT, and consequently the presentation of larval abundance is changed from this year onwards.

The catchability of the MIK at night is close to 100%

(P. Munk, unpublished results), therefore the catches can be used to estimate absolute abundance:

Density (no m·~

=

(no caught/ (distance towed* net opening))* water depth

The opening of the 2 m wide frame is 3.14 m²^,distance towed is measured by calibrated flowmeters in the centre of the frame.

The number of larvae within a statistical rectangle can then be approximated by multiplying the density with the approximate surface area of the rectangle (309

*

¹⁰⁷

m²). The total number of larvae (MIK-index) is then the total of all sampled statistical rectangles. The IKMT catches from this and previous years are converted to MIK catches. This is based on studies comparing the gears, information available from this year and from earlier studies.

HERRING

In all 315 hauls were made. High densities were found in most of the sampled area. A remarkable high abundance was observed in the northern and north-eastern areas (Figure 6.1). The abundance was much higher than in the previous two years (compare to Figures 6.2 and 6.3). The index value (Table 6.1) of 200.7 is of a size that equals the 'good' years in the mid-eighties.

4

Very few sprat larvae were caught and no interpretation of their distribution is made.

7 HYDROGRAPIDC DATA 7.1 Hydro-chemistry Survey

Seven ships contributed hydrographic data to the 1992 data set. The data set consists of 392 stations worked between 13 January and 26 February. Nutrient data were supplied for 142 of these stations, contributions being received from 3 ships. Past nutrient data collected during the IYFS provided an essential contribution to an investi- gation of North Sea nutrient trends for the purposes of the North Sea Task Force, and these new data will provide the basis of future similar studies.

Charts of the distribution of bottom temperature and salinity are given in Figures 7.1 and 7.2. An updated table giving the time series of temperature and salinity at 10 locations in the North Sea during IYFS surveys from 1972 to 1992 is provided as Table 7 .1. The Figures and Table show that oceanographic conditions in the North Sea were very similar to those observed in every year since 1988. This reflects the continuing sequence of very mild winters with frequent westerly type weather. The clear presence of very high salinity water in parts of the Southern Bight in 1991 continued in 1992, but at some- what lower salinity (>35.5 in 1991 and <35.35 in 1992). This appears to be a consequence of rather per- sistent, but unusual, oceanographic conditions in the English Channel.

7.2 UKDMA

Contour maps of all IYFS hydrographic and chemical data since 1970 have been incorporated into a digital computer-based atlas produced by the British Oceano- graphic Data Centre in Bidston, England. UKDMA (UK Digital Marine Atlas) incorporates many different types of data sets involving most marine disciplines, including fisheries, and is available for use on IBM compatible PCs at modest cost.

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8 REFERENCES

Anon., 1989. Report of the International Young Fish Survey in the North Sea, Skagerrak: and Kattegat in 1989. ICES Doe. C.M. 1989/H:54.

Anon., 1991. Report on the International Bottom Trawl Survey in the North Sea, Skagerrak: and Kattegat in 1991: quarter 1. ICES Doe. C.M. 1991/H:S.

Anon., 1992. Manual for the International Bottom Trawl Survey. Addendum to ICES Doe. C.M. 1992/H:3.

Pedersen, L., 1989. International Young Fish Survey, computation of aggregated standard tables and charts.

ICES Secretariat, section computer management.

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Table 3.1 Data available in the ICES IYFS data base as at 1 August 1992

+

Data available

No data available

X No survey made or survey not valid

Country 1972 1973 1974 1975 1976 1977 1978 1979 1980

Denmark

+ + + + + + + +

^X

France X X X X

+

^X ^X

+ +

Germany

Netherlands

+ + + + + + + + +

Notway Sweden UK England

UK Scotland X X

+ + + + + + +

USSR X X

+ + + +

^X

+

^X

Country 1981 1982 1983 1984 1985 1986 1987 1988 1989

Denmark X

+ + + + + + + +

France _X

+ + + + + + + +

Germany

+ + + + + + +

Netherlands

+ + + + + + + + +

Norway

+ + + + + + +1

Sweden

+ + + + + + +

UK England

+ + + + + + + + +

UK Scotland

+ + + + + + + + +

USSR

+ +

^X ^X X X X X X

Country 1990 1991 1992

Denmark

+ + +

France

+ + +

Germany

+ + +

Netherlands

+ + +

Norway

+ + +

Sweden

+ + +

UK England

+

^X ^X

UK Scotland

+ + +

USSR X X X

1 No Smalk records for Herring.

6

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Table 5.1

Herring Sprat Mackerel Cod Haddock Whiting Norway pout

Preliminary 1990 IYFS indices for 1-group fish based on a split of the length distribution, indices used by assessment working groups and final indices for the North Sea.

Preliminary 2,158 1,639

16.7 14.3 1,072

766 4,964

Working Group 2,339 1,639

4,964

Final 2,099 1,561

16.0 13.0 1,115

916 5,121

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Table 5.2 IYFS indices for 1- and 2-year old fish of various species. Indices in mean number per hour within the relevant standard area in the North Sea.

00 ^··-···-Year class - - · · - · · ----~ 1-ring Herring _.I 2-ring¹_ .. age 1 Sprat

I

^{age 2} ^{age 1}Mackerel

I

^{age 2} ^{age 1} Cod

I

^{age 2} ^{age 1}Haddock

I

^{age 2} ^{age 1}Whiting

_I

age_2 age 1 Norway Pout

I

^{age 2}

1969 2,647

-

- -

- - -

25.9

-

32

-

31

1970 1,629

- - - - -

98.3 34.5 855 299 274 190

1971 827

-

⁹⁰

- - -

4.1 10.6 740 971 332 763

1972 1,195 - 123

- - -

38.0 9.5 187 llO 1,156 496

1973 1,592

-

⁴⁸¹

- -

0.1 14.7 6.2 1,092 385 322 153

-

^2,412

1974 452 - -

-

16.5 0.2 40.3 19.9 1,168 670 893 535 4,242 385

1975 342 0 1,186

-

^0.4

₊

7.9 3.2 177 84 679 219 4,599 334

1976 575

-

¹³⁶

-

^1.4

₊

36.7 29.3 162 108 418 293 4,813 1,215

1977 139

-

^1,474

-

2.3

+

^12.9 9.3 385 240 513 183 1,913 240

1978 535

-

²⁴⁸ - 0.2

+

^9.9 ^14.8 480 402 457 391 2,690 61l

1979 551

-

^1,402

- + +

^16.9 25.5 896 675 692 485 4,081 557

1980 1,293 106 886

-

0.1 0.1 2.9 6.7 268 252 227 232 1,375 403

1981 1,797 149 183 461 0.1 5.2 9.2 16.6 526 400 161 126 4,315 663

1982 2,663 712 512 335 1.9 0.4 3.9 8.0 307 219 128 179 2,331 802

1983 3,416 648 347 295 0.1 0.0 15.2 17.6 1,057 828 436 359 3,925 1,423

1984 3,667 853 659 101 0.7 2.1 0.9 3.6 229 244 341 261 2,109 384

1985 5,717 3,857 72 71 0.5

+

^17.0 28.8 579 326 456 544 2,043 469

1986 4,192 816 807 1,433 8.9 0.1 8.8 6.1 885 688 669 862 3,023 760

1987 3,468 470 145 442 1.2 1.8 3.6 6.3 92 97 394 542 127 260

1988 2,146 913 4,246 557 1.1 1.2 13.1 15.2 210 114 1,465 887 2,079 773

1989 2,433 505 177 116 35.0 0.2 3.4 4.1 219 131 509 675 1,320 677

1990 2,099 1,121 340 6.9 0.4 2 . .4 4.5 679 371 1,014 748 2,497 902

1991 1,561 16.0 13.0 1,115 916 5,121

1Total North Sea.

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Table 5.3 Age composition of the standard species in 1992 within the relevant standard area in the North Sea.

Age group 1 2 3 4 5 6+

Herring 2098.7 663.1 229.4 28.0 53.6¹

Sprat 1560.5 340.2 37.8 5.5 ^0.41

Mackerel 16.0 0.4 2.2 1.1 0.0 0.0

Cod 13.0 4.5 1.2 1.0 0.3 0.5

Haddock 1115.0 370.7 18.8 2.9 0.5 2.0

Whiting 915.9 748.1 260.5 168.9 16.0 14.3

Norway pout 5120.7 902.3 33.4 4.7 0.0 0.2

1Plus-group.

Table 5.4 IYFS indices for herring and sprat in Skagerrak-Kattegat. The herring indices are weighted by the area of four depth strata. and the sprat indices are the mean by hour within the total area.

Herring

Sprat

Year Total Spring-spawners Autumn-spawners

1-ring

I

^2-ring ^1-ring

I

^2-ring ^1-ring

I

^2-ring ^1-group

I

^{2 +group}

I

^Total

1974 1,325

1975 5,339

1976 2,069

1977 5,713 984 6,697

1978 5,119 2,117 7,236

1979 3,338 1,482 4,820

1980 2,311 387 1,607 307 704 80 4,960 3,592 8,558

1981 3,246 1,393 966 1,318 2,250 75 2,809 3,068 5,877

1982 2,560 549 1,408 445 1,152 104 1,577 4,695 6,272

1983 5,419 1,063 1,522 946 3,897 117 1,173 1,685 2,858

1984 6,035 1,947 2,793 1,419 3,242 528 4,141 2,216 6,357

1985 7,994 2,473

-

¹ 1,867

-

¹ ⁶⁰⁶ ^2,077 ^2,067 ^4,744

1986 21,489 2,738

-

¹ 1,562

-

¹ 1,176 684 4,834 5,518

1987 11,733 3,671

-

¹ ^2,921

-

¹ ⁹⁴⁹ ^1,830 ^16,543 ^18,373

1988 67,753 10,095

-

¹ 7,834

-

¹ ^2,161 ⁹⁴⁵ ^8,238 ^9,183

1989 17,451 4,976

-

¹ ⁰

^-

^I ^4,976 ⁴⁴² ^2,891 ^3,333

1990 3,544 3,876 0 3,192 3,544 684 503 471 974

1991 3,588 3,794

-

¹ ⁴⁸⁰

^-

¹ ^3,269 ⁶⁹³ ^1,245 ^1,938

1992 5,057 1,934 0 771 5,057 1,163 5,380 1,698 7,078

1Separation not valid.

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Table 5.5 Indices of 1- and 2-group cod and 1-group whiting and haddock in Skagerrak-Kattegat. The preliminary indices are the mean number per hour for cod

<

25 cm, whiting and haddock

<

20 cm.

Cod 1-group Cod 1-group Cod 2-group Whiting Haddock

Year

Skagerrak Kattegat 1-group 1-group

Class Skagerrak Kattegat

Prel. Final Prel. Final Prel. Prel.

1974 499

1975 236

1976 99

1977 392

1978 561

1979 79 386 93 171 722 40

1980 18 15 42 26 31 63 968 4

1981 36 36 126 104 30 258 690 48

1982 32 28 113 96 19 143 262 34

1983 24 23 49 39 52 106 500 72

1984 18 14 18 9 10 72 940 161

1985 82 78 229 213 113 372 1,379 57

1986 15 5 48 11 18 28 2,178 251

1987 81 77 76 68 24 48 2,978 125

1988 62 56 6 3 8 16 478 20

1989 25 31 131 153 25 112 2,255 8

1990 42 9 39 19 5 20 1,636 74

1991 119 96 64 64 1,796 288

10

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Table 6.1 Density and abundance of herring larvae caught in February during the IBTS. Values for year classes by areas are density estimates in number per square metre. Total abundance (MIK-index) is found by multiplying density by surface area and adding up (see also text).

Area North North Central Central South South Division Southern 0-ringers

west east west east west east Ilia Bight abundance

Area m²x 10⁹ 83 34 86 102 37 93 31 31 N in billion

Year Class

1976 0.054 0.014 0.122 0.005 0.008 0.002 0.002 0.016 17.1

1977 0.024 0.024 0.050 0.015 0.056 0.013 0.006 0.034 13.1

1978 0.176 0.031 0.061 0.020 0.010 0.005 0.074 0.000 52.1

1979 0.061 0.195 0.262 0.408 0.226 0.143 0.099 0.053 101.1

1980 0.052 0.001 0.145 0.115 0.089 0.339 0.248 0.187 76.7

1981 0.197 0.000 0.289 0.199 0.215 0.645 0.109 0.036 133.9

1982 0.025 0.011 0.068 0.248 0.290 0.309 0.470 0.140 91.8

1983 0.019 0.007 0.114 0.268 0.271 0.473 0.339 0.377 115.0

1984 0.083 0.019 0.303 0.259 0.996 0.718 0.277 0.298 181.3

1985 0.116 0.057 0.421 0.344 0.464 0.777 0.085 0.084 177.4

1986 0.317 0.029 0.730 0.557 0.830 0.933 0.048 0.244 270.9

1987 0.078 0.031 0.417 0.314 0.159 0.618 0.483 0.495 168.9

1988 0.036 0.020 0.095 0.096 0.151 0.411 0.181 0.016 71.4

1989 0.083 0.030 0.040 0.094 0.013 0.035 0.041 0.000 25.9

1990 0.075 0.053 0.202 0.158 0.121 0.198 0.086 0.196 69.9

1991 0.255 0.390 0.431 0.539 0.500 0.369 0.298 0.395 200.7

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-

N

~ - - - - - - - - · - · · · - - - - - - - ---~---~--

Location 1 2 3 4 5 6 7 8 9 10

Position 60° O'N 57° 30'N 57° 30'N 57o 30'N 55° O'N 55° O'N 55° O'N 55° O'N 54° O'N 52° 30'N

2°E ooE 2°E 4°E ooE 2°E 4°E 8oE 3°E 3°E

Year toe J S-30 toe

I

^S-30 ^toe

I

^S-30 ^t⁰e

I

^S-30 ^t⁰^e

I

^S-30 ^toe

I

^S-30 ^toe

I

^{S-30 toe}

I

^S-30 ^toe

I

S-30 tocJ S-30 1972 5.8 5.22 6.9 5.08 5.9 5.20 4.5 4.78 6.5 4.91 4.8 4.86 5.2 4.80 2.5 3.80 5.2 4.70 6.9 5.10 1973 7.4 5.02 7.2 5.20 6.7 5.10 7.0 5.05 6.1 5.00 6.0 4.86 5.0 3.00 6.4 4.80 6.5 5.05 1974 6.9 5.28 6.5 5.11 6.5 5.08 6.3 5.04 6.5 4.90 6.0 4.90 5.6 4.90 4.7 3.00 6.1 4.78 8.0 5.20 1975 7.3 5.20 6.6 5.05 6.6 5.15 6.4 5.13 6.6 4.95 6.4 4.90 6.1 4.85 5.2 3.50 5.9 4.62 6.9 4.62 1976 6.7 5.20 6.5 5.00 6.5 5.15 5.6 5.12 6.1 4.81 4.9 4.95 4.9 4.85 2.2 1.00 5.1 4.78 5.1 4.80 1977 6.0 5.18 6.2 5.02 5.1 5.00 4.8 4.92 6.0 4.98 4.9 4.85 5.0 4.80 3.1 3.60 5.6 4.78 7.1 5.22 1978 6.4 4.88 6.6 5.00 6.0 4.90 4.7 4.88 5.6 4.78 4.9 4.88 4.2 4.80 2.2 2.50 4.6 4.68 5.5 4.90 1979 6.4 5.15 6.0 4.80 4.1 4.88 4.0 4.98 4.5 4.64 2.8 4.62 2.8 4.62 -1.5 2.00 3.0 4.62 4.2 4.95 1980 5.9 5.12 6.6 5.00 5.5 5.00 4.5 4.70 6.1 4.60 3.8 4.65 4.5 4.50 3.1 3.50 5.1 4.70 6.1 5.11 1981 6.9 5.22 6.6 4.90 6.2 5.05 5.8 5.15 6.5 4.80 5.8 4.82 5.1 4.82 3.4 2.50

1982 6.6 5.28 6.1 5.02 5.9 5.05 5.5 5.10 5.5 4.72 4.8 4.82 4.5 4.62 2.8 2.50 4.7 4.30 6.0 4.65 1983 6.9 5.22 6.5 5.00 6.4 5.10 6.2 5.15 5.6 4.62 6.1 4.95 5.2 4.90 3.0 3.00 5.2 4.80 6.4 4.70 1984 6.3 5.18 6.4 5.10 6.4 5.10 5.2 5.12 5.9 4.80 5.0 4.84 4.9 4.90 3.5 3.00 4.9 4.65 7.4 4.95 1985 6.9 5.17 6.8 5.10 6.5 5.18 5.9 5.05 6.5 4.70 4.7 4.91 5.0 4.90 1.0 2.50 4.0 4.70 6.0 4.80 1986 6.6 5.25 5.8 5.05 5.4 5.08 5.2 5.05 5.2 4.65 3.9 4.72 3.6 4.60 0.0 2.50 4.0 4.60 4.0 4.65 1987 6.5 5.28 6.1 4.90 5.9 5.08 4.9 5.00 5.0 4.75 4.2 4.80 4.3 4.60 0.8 0.00 4.9 4.60 4.8 4.90 1988 7.6 5.18 7.6 4.95 7.4 5.03 7.0 4.96 7.1 4.70 6.6 4.80 6.5 4.50 5.9 3.50 6.9 4.60 7.7 4.90 1989 8.5 5.29 8.0 4.85 7.8 4.89 7.6 5.05 7.5 4.76 7.1 4.81 6.8 4.80 6.0 4.10 6.5 4.68 7.5 4.62 1990 8.5 5.29 7.6 5.00 7.6 5.12 7.6 5.15 7.5 4.70 7.5 4.85 7.5 4.80 6.5 4.10 7.4 4.70 7.4 4.60

I 1991 7.9 5.30 6.7 5.10 7.1 5.22 6.1 4.97 6.6 4.65 5.8 4.85 5.5 4.80 3.0 4.00 5.8 4.60 6.1 5.30

I 1992 8.1 5.29 7.6 5.10 7.1 5.16 7.1 5.19 7.4 4.80 6.6 4.80 6.5 4.80 6.6 2.00 4.5 4.80 6.0 5.20

TABLE 7.1 Time series data of bottom temperature and salinity during IYFS 1972-1992

(17)

International Young Fish ^Sur\·sy 1992

E5 E6 E7 E8

1

...

_c. ₁ ⁵¹

2 ; 2 50

2 2 49

2 ' 1 2 48

2 47

1 2 46

45 44

0

57

40 39 38 37 36 35 34 33 32 31

0

51 30

29 28

Figure 5.1 Number of hauls used in the analysis of herring data 1992.

(18)

59°

58°

0

57

•o

51

50

E5 CG

----,-- ---

.

^~

r 7 L I

~Pc?

~~-~

'\};~ 2

~----~- 2 ..

2---~

2

3

2

F5 F6 F? F8 F9 GO G1 G2

2 2 2 2

2 2 2

2 2 2 2

3 2 2 2

- t ^~

:

2 2 2 2

2 2 2 3

~- !

2 2 3 2

Date of Production: JUN 18, 1992

Figure 5.2 Number of hauls used in the analysis of data on sprat, mackerel, cod, haddock, whiting and Nmway pout 1992.

14

52

51

50 49 48 47 46 45 44 43

42

41 40 39 38 37 36 35 34 33 32

31

30 29 28 27

(19)

International Young Fish Survey 1992

E5 E6 E7 E8 E9 FO F1 F2 F3 F4 F5 F6 F7 F8 F9 GO G1 G2

-==r--

I ====t-

li_i_

1 I

__[__ ^- ·-- ^{- -}^{[ _}

52

1

o i ^o¹

J- ^!

_I

6ti - ---,----

lt'.~

^1:;::1

^oi

^'

- - - - - - - ~-

0 (1

f

<J I I

--- - 1 - - _, I

0 ^!

0 51

50 49 48

0

.j._ ~-- ^{I - -} ~--- ^-

o ; . I

~~01' ¹ o I o · o i

--¥- : ---~----: _ ^{i _}

n~~ ~---~-~--J---1--~l-

⁰

^_L_

⁵

1 1 \ I 9!

o;

¹ ^1j

--t---i-r----;---:

I I

~-~--u36

^! ^, ^_⁰

!

I 3j 2i 1 5 0

-t---;----t---- '

---+---+--~---+---t---___,...,~,P'\

1 50 I 5 ¹ 102 1

47 46 45 44 43 42

0

19 0

3 3 8

0 37 0 21

1783 I 2258 499

8381 4962 2545 262 41

83 3 2 8 1576 15005 256 40

648 1 I 631

I

⁹¹⁸⁴ⁱ³⁶⁸⁷ ⁶⁴⁵ ³⁹

812 212 960 1695 38

9 272 884 87691 7649 1064 363 I 37

150 2191 2389 2388 36

7603 193 35

44 505 34

33 32

0

31

.51

30 29 28 AUG 10, 1992 27

100 12°

Figure 5.3 Herring: number per hour, 1-ringers.

(20)

E5 E6 E7

0

57

International Young Fish Survey 1992

E8 E9 FO F1 F2

6f

i

!lf ^o!

^{- -}⁴²^oi

^--r

ⁱÎÎ,_ Î

11 '

lfr-

i

l

i

1 I

65 ^I 19 0

:

· - + I I

3 27 ^I

I

⁰ ⁰

i

I

t--

0 ^I

0 - - + - - - -

, I t "

- - -

19 ! ⁰

I

¹⁴^I ⁴²

0 !

0

2

F9 GO

0 48 0

i I

1033 I 39 · 209

!

4 1 65

!

²⁹⁷¹ ⁵ ⁴

~~~~--~--~--~--~--~-~---·~' --·~~~~~~

2

I

²¹ ²¹⁶! 472 13 I

Figure 5.4

16

62 2 41

108 1654 41 589 I ^I 167

--~--~---+----~----r·---4----~--4---~~~

! 160 844 15

41

~--~--~--~ ^I

1251 : 4051

I I

I

10 204 405

58 0 249 1164

44 4904 144 2 7885

Herring: number per hour, 2-ringers.

G1 G2

47

4 46

45 44 43 42 41 40 39 38 37 36 35 34 33 32 31

30 29 28 1992 27

12°

(21)

International ^Your1g

^!='^I ^1'^C)^~--

^h

E5 E6

6t

---r----~ ----

! - ~--· ^····f186

0 ~17 ^?

⁷⁸

60o !+----~---~---- ~ ^- ^{I -- - -}

1232

44

10

0 651 14

2819 '

11

868 32 2

990 6

16 i

2)

I

115 ^{0 '}

0 I ~ 4964

41

!

⁹

0 !

i o o I

i I

,-~--,--~-

I

51

0 i 5 I o ^[I

·---t---11---"""4--- ^I I +-~-+--

0

1

13 i

Figure

5.5

Herring: number per hour, 3 +ringers.

1992

48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27

(22)

International Young Fish Survey 1992

E5 El E8 E9 F5 F6 F7 F8 F9 GO G1 G2

52 51

50 49 48 47 46 45 44

5l

43

42 41

56 i162 !160 ₁162 i169 j163j171F6o 151 40

167 152 39

38 37 36 35 34 33 32 31 30 29 28 Date of Pr'oduct 'Jn: AUG 10, 1992 27

6 ll

Figure 5.6 Herring: mean length, 1 -ringers.

18

(23)

International Young Fish Survey 1992

E5 E6 E7 E8 E9 FO F2 F4 F5 F6 F7 F8 F9 GO G1 G2

52

l- 1--

0 ' ⁰ 0 : 0 0 ' 51

0 I 0 50

-- +- ----:--I

60 ol

49 48

I

0 0 ' 0 :

- --t---1 -

I I

0

47 46 45

58°

0 0 0 44

0 0 0 0 43

57°

0 0

sj

¹⁵ ⁴ ⁴²

I

0 ! 13 0 205 31 41

8 0 0 0 0 0 612 94 40

I 39

0 27 0 56 2386 794 2590 1249

1375 740 0 16965 5758 187 33 38

16 28 1457 35824 43 576 404 37

11270 7149 12420 1713 36

7060 349 35

34 33 32 31 30

29 28 Date of Production: JUN 18, 1992 27

12°

Figure 5.7 Sprat: number per hour, age group 1.

(24)

International Young Fish Survey 1992

E5 E6 E7 E8 E9 FO F1 F2 F3 F4 F5 F6 F7 F8 F9 GO Gl G2

L

0 0 0 0

0 0 0 0 0

o I 1 o · o . o ! o o o o

j-L·----r-:

- - + - - - + - - + ----+--

o 5 1 o o o o ¹ 3 0

42 14 0 o I 9 I o 9 1

I

35 0 1 0 3 25 89 6

197 40 0 13 247 257

I

^77o

2933 2893 24 470 439 33 87 102 684 2840 15 30 131 '

1314 4466 1777 833 3199 46

0

51

Oat:.- of Production: ,JtJ~J 18 .1992

Figure 5.8 Sprat: number per hour, age group 2.

20

52 51

50 49 48 47 46 45 44 43 42 41

40 39 38 37 36 35 34 33 32 31 30 29 28 27

(25)

6{

60°

58°

yf

International Young ^Fish

^C:!J_~

^{r· \'}

I\__...)' t:::C \ (

1992

rr===~===+===+==~====~==+===~==~==~==~~~====r=r===r==L===r===~===c===c==~

i ~-

j_

I I ^! I

0 : 0 : ⁰ ⁰¹

-+-~

0 ^!

oi

i

0~·~

- -~-

0 0

---+-~-~~

0 ^I^II 0

~l- ·)~

. - - - + - - - -

I 0 i ⁱ 0 ^{0 I}

.•. };

I I I - - - , ---r---^' ^I ^~,....

----t--

o

I

0

I

^o^I ⁰ⁱ ⁰

I

^I

4

⁰ⁱ^! ô₀Î_! ^~----ôÎÎ ⁰ ^{_ _j__}ÎÎ

1 i o I _{0 I} ₀

I

⁰ ⁰ ⁰

I

o

I

^{0 '} ⁰

L---

I ^{0 :} ⁰ ⁰ ⁰ ⁰

0 0 ol

I

⁰

I ol

o I ⁰ ⁰

6 0 0 0 3 2 1

54 5 0 12 47 5

654 324

49H

⁴ ⁵³

21 481 436 1 1 27'

I

112 217 125 77

201 13

17 1638

52 51

50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30

29 28

D at e o f F'" o d u c t i on: J UN 18. 19 9 2 27

Figure 5.9 Sprat: number per hour, age group 3

+.

(26)

International Young Fish Survey 1992

0 0

0 0 0

80 0 0 0 0 0

I

87 0 ⁱ 0 0 0 0 0

89 0 0 0 87 90 87

96 0 0 94 0 85 81

0 0

o

102 107 1 93 84

107 81 0 90 85 88 91

87 90 0 72 i 80 84

88 86 86 75 85 I 83

79 89 82 84 83 81

72 0

Figure 5.10 Sprat: mean length, age group 1.

22

52 51

50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28

;!_{

(27)

International Young Fish Survey 1992

E:.5 E6 E7 E8 E9 FO F1 ^l-·n^{r·· /} F3 F4 F5 F6 F7 F8 F9 GO G1 G2

0

57

~ j' \· Q ¹ 2 ' 100 ---+-~---1 ^- ^- J: ~ ~ ~ --- ^{+- -}

I 11 ,

I

1 ~m: ^{0 ;} ⁰

· -- - ~ r ~~w."' ^o

^L--2----'--- ----+---

~-...-~f+- ~

^{I --.----} ⁰ ¹¹

1

I O! 2 ¹ 1 0 ₁ 0 9

---t

r-

^--~

~.

^{0 • 0}

~ _a ~

^5_4

-+---+-~

" f r - - - -

-~--1---o

^{-+-- -}

~l~o-1~ --~~ _o--f"""'"""""'"l--~

0 0

i

0 118951175

----:~--+---+----

-

----+---1""""""""'""'1---=--f!J~.L...-f----11---t---+-~

-~ --~~~; ^_oJ_oj__o

^J.

_o-+--o-+--3~-""""'l'-"""""'1f----+----l

1 • I I

i

1 0 i 0 1 0 1 : 0 0 0 0 0

, - - 1

--~J ~ ^t ~r--or_-

0--l---0 +-I - - + - 0 + - - - 1 - - - H

I :

Î Î Î

~

^oⁱ ^{o :} ^o

1

1 ! 10 ^I o o

. ! I

1 o ^I ⁰

o

^I

o

I ⁰ ⁰

01

i

0 2 0

0 0

0

ol

Date of Production: JUN 18,

•• -. r -----~- -..,.- - - --~

- -J -·-·- ---~ -·--. -- =~-=~-:--== =-:.=r:::::--==-=-..,__:_-::::_

10

Figure 5.11 Mackerel: number per hour, age group 1.

1992

12°

52 Si

50 49 48 47 46 45 44 43 42 41

40 39 38 37 36 35 34 33 32 31 30 29 28 27

(28)

International Young Fish Survey 1992

E5 E6 E7 E8 E9 FO F1 F2 F3 F4 F5 F6 F7 F8 F9 GO G1 G2 52

0 0 51

50 49 48 47 46 45 44

5l

43

42 41

0 0 0 40

0 0 0 39

0 0 0 38

0 0 0 37

0 0 0 0 36

0 0 35

0 4 34

33 32 31 30

Figure 5.12 Mackerel: number per hour, age group 2.

24

(29)

E5 E6

58°

5l

Figure 5.13

I n t e r n a t i o n a l Y o u n g F i s h S u r

'v.

e ^y ^{1 9 9 2}

E7

52 51

50 49 48 47 46 45 44 43

40 39 38 37 36 35 34 33 32 31 30

29 28 Date of Product ion: JUN 18, 1992 27

-:-~~---=--.:_:::I,;--:=.:__:__·---:; -=~=:=:-=r-===-.r:=.--T --==---_)

l(f 12~

Mackerel: number per hour, age group 3

+.

(30)

International Young Fish Survey 1992

- r

!: 0 215 ' 208 ^I 235

---1i~-

-

^--j

I ^19~ ill

⁰ ^I ^{0 :}

: -i ^~" .

^l^{225 '} ⁰

60°

H---~-+---.,0...-...1!--' -~-1-"-~---

⁰^{- t}

-t

1 1 228 : 295

- - --+---H - -

t . --

0 ! 59°1-4---i----L ~--+---~

0 185

57

50

--+ I

0 i

!

F8 F9

0·

205 ' 0

I

o l o I

²¹⁴

--~+--+---+--=~~=-+--

0 ! 0; 0

' I

Figure 5.14 Mackerel: mean length, a~) group l.

26

GO G1 G2

52 51

50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28

(31)

International Young Fish Survey 1992

E5 Ef> E7 E8 E9 F-0 F1 F2 F3 F4 F5 F6 F7 F8 F9 GO ^G1 ^G2

·-_--,-+=-=.::::I--==-

_,__:::=::J=== ::L----==r= _=r_-::::--::.==:+:====+=t==-=---jr-=t:;::::==:::r::===r:===c::==::r=::::r:==:=:=r:==c===r::===::r====r===~

I

i ~-,

-~ -+~

0 0 0 40 ^I (>~

-~~~

~r~

6t I

fl~·· ;

⁰

^~~··

60,! I . -•-

. - t ^5f~ -

⁰

-~ -- ~___j:

²^I ^{0 ,}

- L

0 0 ^! 12 0 27 10 I

I

-t ^j

0 10 1

l

⁵²

-- l

52 51

50 49 48

6 0 1 ^Il 0

3 ' 0 47

0

^I ^{- - - -}^+-^- --~

0--r

--1~- ^{- ;}

I __;__ _ _ ; _ -

-1

----l-·---J.--"'-

3 ~ 2 4 : 0 : 0

I

22 4

i ^I

- - - - + , - - - --,---

----r

·---<-~----,---t-·-·- -~=~----+--....::::..::f'tP=>.AL:::.P..."""""',..,_,""""""..._---1~

~-~ 1 i~~-it~:r~:~-::~HK~~~- ¹ :_j~r---_,.,o¥-~'-

~ I ^I ^I ^' I

- ) 1 ' : 0 ' 9 : 12 : 10 I 5 20 12

I - 4 - - ^I ~----r: --+·---~----~-4----HK

2 !

_:J----~-1-~!

⁵

^!

²⁵ ^13\ ²²

0 •

-~9_l_ 1~1

⁴

I 11 ^I

⁹

^L ^__

11-+-i _1_8 +---6-+---+--fl--J.

1

~9 ^! 4~:~-1~+~-

^-6-+-\--5+---+---+-___JJ_'-dl 1

461 ~1~~2!

⁷

ⁱ

¹

11 : 0; 1 i 7

I

0

57

C•

54

46 45 44 43 42 41

40 39 38 37 36

6

4 35

0 2 34

33 32 31 30 29 28

.JU~J 1 f. 1°92 27

-·-{---+---<.

1 ___) 4 I

/ ^~~~j-

.~--4'-v. : : ⁱ ^; ^j

' -- ----~--- --~- ---1---+---~

--::b

I : ;')--F' ' ; ~/"'"

---- -r---r -zri ~_

V=--=-.-

^-b~

i .

^~ ^{q \} ^---/ ^{Date of} Productio~:

~ ·--_ :::..::..:..:::r:::.== .. -1:~::-.:::::-.:.:::1:::::::}:-:::: .::T.-:::-.:::.::::::::r:-::·-==r::::::::·-=r:...:._==:::r--===:r=::--=r=-:r--:r:

4'· { o' ^2° ^l ^6°

Figure 5.15 Cod: number per hour, age group 1.

(32)

International Young Fish Survey 1992

E5 E6 E7 E8 E9 FO F1 I !

1 - + - - - f - -r---

0 26

5l

0

Figure 5.16 Cod: number per hour, age group 2.

28

19

48 47 46 45 44 43 42

41

39 38 37 36 35 34 33

~ ,J2

1 31 30 29 28

? r o d u c t i on: J U ~J 16, 1 9 9 2

J

27 -=:.-::.r-==.:.=_J

12,

(33)

5l

53°

I n t e r n a t i o n a l Y o u n g r-- i s h s u :' '/ e y 1 9 9 2

E5 E6 E7 ^F6 ^F7 ^F8 ^F9 ^GO ^G1 ^G2

-r ^-

10

2 32

0

-·-

^I

4

¹

---

+

2

ⁱ ⁰ _i

4

- - - - r - - - - -^~~

G~~

⁰ ⁶ ⁶ ⁴^! ⁶

~

⁴

1:1 /:;)

-+----,,

--~-.

----t- - -r-

--i----+--~~

I ^I I

0

^I

2 1

^I

4

^I

2 ^l 4 2

¹³

6

2

^I

-~+~-~ ² 1~ ~_j ^__ s:~-4

"""'""--/_,:_.._y_-=..--:.:--! 1 ^I ^__2_j ^a ^! 1 ^! 2 ~2::~~3~:===:==::::::~:~:---.:~--~

I

i 0 1 0 01

4

^I

2 I 4 2 24

----~-~-1---r--;----+---+----+---+---+----Jr--,~!-''y"'S-r"

3

oJ o o

0 ¹ 3! 2 1

1-=-"'---+---+---+---J 0 3 !

o I

¹ ⁰

1 2

~1+.

37

¹ ¹ ⁹

3

5

2

_I^I ⁰

2 2

⁷ ⁰ ¹

0

3

1

Figure 5.17 Cod: number per hour, age group 3

+.

52 51

50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30

29 28

(34)

58 0

5l

0

51

4

Figure 5.18

30

International Young Fish Survey 1992

285 I 135

i ⁰ ⁰ ¹³¹ ¹⁶⁸

155 2651

0 0 152 174 152 213 150 157 \ 137 119 128 229 231

0 136 153 163 135 I 205 185

o

157 174 I I 136 195 145 153

190 215 167 189 177 162 165 127 166 176 155

165 161 204

178 161 173

155 1491 143 139 163 182

158~206

0 150 174 168 165 185

0 187

174 194

F8 F9 GO G1 G2

52

51

50 49 48 47 46 45 44 43 42 41

40 39 38 37

36

35 34 33 32 31 30 29 28 Date of Product ion: JUN 16, 1992 27

2

Cod: mean length, age group 1.